1. Field of the Invention
This invention relates to a sensor assembly for measuring the weight applied to a vehicle seat.
2. Related Art
Most vehicles include safety devices such as airbags and seatbelt restraint systems, which work together to protect the driver and passengers from experiencing serious injuries due to high-speed collisions. It is important to control the deployment force of the airbags based on the size of the driver or the passenger. When an adult is seated on the vehicle seat, the airbag should be deployed in a normal manner. If there is an infant seat or small adult/child secured to the vehicle seat then the airbag should not be deployed or should be deployed at a significantly lower deployment force. One way to control the airbag deployment is to monitor the weight of the seat occupant.
Currently there are various types systems that use different types of sensors and mounting configurations to determine seat occupant weight. For example, some systems use pressure sensitive foil mats or a plurality of individual sensors mounted within a seat bottom foam cushion. One disadvantage with this type of system is that mounting the sensors within the cushion can be difficult and time consuming. For example, it is difficult to find sensor mounting locations within the cushion that will sufficiently accommodate all of the various positions of a seat occupant while still providing accurate measurements. Further, shifting of the occupant on the seat can dislodge or move the sensors out of their proper location, which compromises the accuracy of sensor measurements. Also, because the sensors are mounted within the cushion, it is difficult to reposition or replace the sensors after the seat has already been installed in the vehicle.
Another type of system mounts sensors between various structural components on a vehicle seat, such as between a seat frame member and a seat track. The sensors include a strain gage mounted on a bendable or deflectable body portion that measures the amount of strain in the deflectable body portion resulting from a weight force being exerted on the vehicle seat. The strain measurements from each of the sensors are combined to determine the total weight of the seat occupant. One disadvantage with this type of system is that due to the structural mounting configurations and requirements for seat assemblies, it is difficult to have accurate strain measurements at the lower strain ranges. In other words, because the sensor assemblies are connecting elements between the seat frame member and seat track member, the sensor assemblies must be strong and durable enough to provide secure connection point within the seat assembly but must also be able to provide a sufficient amount of bending/deflection so that the strain gages can measure strain accurately over a wide range of occupant sizes.
Thus, it is desirable to have an improved seat occupant weight measurement system that provides increased accuracy as well as overcoming any other of the above referenced deficiencies with prior art systems.